package com.itsq.utils;

import org.springframework.util.Base64Utils;

import javax.crypto.Cipher;
import java.io.ByteArrayOutputStream;
import java.security.*;
import java.security.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import java.util.HashMap;
import java.util.Map;


/**
 * <p> 
 * RSA公钥/私钥/签名工具包 
 * </p> 
 * <p> 
 * 罗纳德·李维斯特（Ron [R]ivest）、阿迪·萨莫尔（Adi [S]hamir）和伦纳德·阿德曼（Leonard [A]dleman） 
 * </p> 
 * <p> 
 * 字符串格式的密钥在未特殊说明情况下都为BASE64编码格式<br/> 
 * 由于非对称加密速度极其缓慢，一般文件不使用它来加密而是使用对称加密，<br/> 
 * 非对称加密算法可以用来对对称加密的密钥加密，这样保证密钥的安全也就保证了数据的安全 
 * </p> 
 *  
 * @version 1.0 
 */  
public class RSAUtils {  
  
    /** 
     * 加密算法RSA 
     */  
    public static final String KEY_ALGORITHM = "RSA";  
  
    /** 
     * 签名算法 
     */  
    public static final String SIGNATURE_ALGORITHM = "MD5withRSA";  
  
    /** 
     * 获取公钥的key 
     */  
    private static final String PUBLIC_KEY = "RSAPublicKey";  
  
    /** 
     * 获取私钥的key 
     */  
    private static final String PRIVATE_KEY = "RSAPrivateKey";  
  
    /** 
     * RSA最大加密明文大小 
     */  
    private static final int MAX_ENCRYPT_BLOCK = 117;  
  
    /** 
     * RSA最大解密密文大小 
     */  
    private static final int MAX_DECRYPT_BLOCK = 128;  
  
    /** 
     * <p> 
     * 生成密钥对(公钥和私钥) 
     * </p> 
     *  
     * @return 
     * @throws Exception 
     */  
    public static Map<String, Object> genKeyPair() throws Exception {  
        KeyPairGenerator keyPairGen = KeyPairGenerator  
                .getInstance(KEY_ALGORITHM);  
        keyPairGen.initialize(1024);  
        KeyPair keyPair = keyPairGen.generateKeyPair();  
        RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic();  
        RSAPrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate();  
        Map<String, Object> keyMap = new HashMap<String, Object>(2);  
        keyMap.put(PUBLIC_KEY, publicKey);  
        keyMap.put(PRIVATE_KEY, privateKey);  
        return keyMap;  
    }  
  
    /** 
     * <p> 
     * 用私钥对信息生成数字签名 
     * </p> 
     *  
     * @param data 
     *            已加密数据 
     * @param privateKey 
     *            私钥(BASE64编码) 
     *  
     * @return 
     * @throws Exception 
     */  
    public static String sign(byte[] data, String privateKey) throws Exception {  
        byte[] keyBytes = Base64Utils.decodeFromString(privateKey);
        PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);  
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);  
        PrivateKey privateK = keyFactory.generatePrivate(pkcs8KeySpec);  
        Signature signature = Signature.getInstance(SIGNATURE_ALGORITHM);  
        signature.initSign(privateK);  
        signature.update(data);  
        return Base64Utils.encode(signature.sign()).toString();
    }  
  
    /** 
     * <p> 
     * 校验数字签名 
     * </p> 
     *  
     * @param data 
     *            已加密数据 
     * @param publicKey 
     *            公钥(BASE64编码) 
     * @param sign 
     *            数字签名 
     *  
     * @return 
     * @throws Exception 
     *  
     */  
    public static boolean verify(byte[] data, String publicKey, String sign)  
            throws Exception {  
        byte[] keyBytes = Base64Utils.decodeFromString(publicKey);
        X509EncodedKeySpec keySpec = new X509EncodedKeySpec(keyBytes);  
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);  
        PublicKey publicK = keyFactory.generatePublic(keySpec);  
        Signature signature = Signature.getInstance(SIGNATURE_ALGORITHM);  
        signature.initVerify(publicK);  
        signature.update(data);  
        return signature.verify(Base64Utils.decodeFromString(sign));
    }  
  
    /** 
     * <P> 
     * 私钥解密 
     * </p> 
     *  
     * @param encryptedData 
     *            已加密数据 
     * @param privateKey 
     *            私钥(BASE64编码) 
     * @return 
     * @throws Exception 
     */  
    public static byte[] decryptByPrivateKey(byte[] encryptedData,  
            String privateKey) throws Exception {  
        byte[] keyBytes = Base64Utils.decodeFromString(privateKey);
        PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);  
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);  
        Key privateK = keyFactory.generatePrivate(pkcs8KeySpec);  
        Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());  
        cipher.init(Cipher.DECRYPT_MODE, privateK);  
        int inputLen = encryptedData.length;  
        ByteArrayOutputStream out = new ByteArrayOutputStream();  
        int offSet = 0;  
        byte[] cache;  
        int i = 0;  
        // 对数据分段解密  
        while (inputLen - offSet > 0) {  
            if (inputLen - offSet > MAX_DECRYPT_BLOCK) {  
                cache = cipher  
                        .doFinal(encryptedData, offSet, MAX_DECRYPT_BLOCK);  
            } else {  
                cache = cipher  
                        .doFinal(encryptedData, offSet, inputLen - offSet);  
            }  
            out.write(cache, 0, cache.length);  
            i++;  
            offSet = i * MAX_DECRYPT_BLOCK;  
        }  
        byte[] decryptedData = out.toByteArray();  
        out.close();  
        return decryptedData;  
    }  
  
    /** 
     * <p> 
     * 公钥解密 
     * </p> 
     *  
     * @param encryptedData 
     *            已加密数据 
     * @param publicKey 
     *            公钥(BASE64编码) 
     * @return 
     * @throws Exception 
     */  
    public static byte[] decryptByPublicKey(byte[] encryptedData,  
            String publicKey) throws Exception {  
        byte[] keyBytes = Base64Utils.decodeFromString(publicKey);
        X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(keyBytes);  
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);  
        Key publicK = keyFactory.generatePublic(x509KeySpec);  
        Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());  
        cipher.init(Cipher.DECRYPT_MODE, publicK);  
        int inputLen = encryptedData.length;  
        ByteArrayOutputStream out = new ByteArrayOutputStream();  
        int offSet = 0;  
        byte[] cache;  
        int i = 0;  
        // 对数据分段解密  
        while (inputLen - offSet > 0) {  
            if (inputLen - offSet > MAX_DECRYPT_BLOCK) {  
                cache = cipher  
                        .doFinal(encryptedData, offSet, MAX_DECRYPT_BLOCK);  
            } else {  
                cache = cipher  
                        .doFinal(encryptedData, offSet, inputLen - offSet);  
            }  
            out.write(cache, 0, cache.length);  
            i++;  
            offSet = i * MAX_DECRYPT_BLOCK;  
        }  
        byte[] decryptedData = out.toByteArray();  
        out.close();  
        return decryptedData;  
    }  
  
    /** 
     * <p> 
     * 公钥加密 
     * </p> 
     *  
     * @param data 
     *            源数据 
     * @param publicKey 
     *            公钥(BASE64编码) 
     * @return 
     * @throws Exception 
     */  
    public static byte[] encryptByPublicKey(byte[] data, String publicKey)  
            throws Exception {  
        byte[] keyBytes = Base64Utils.decodeFromString(publicKey);
        X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(keyBytes);  
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);  
        Key publicK = keyFactory.generatePublic(x509KeySpec);  
        // 对数据加密  
        Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());  
        cipher.init(Cipher.ENCRYPT_MODE, publicK);  
        int inputLen = data.length;  
        ByteArrayOutputStream out = new ByteArrayOutputStream();  
        int offSet = 0;  
        byte[] cache;  
        int i = 0;  
        // 对数据分段加密  
        while (inputLen - offSet > 0) {  
            if (inputLen - offSet > MAX_ENCRYPT_BLOCK) {  
                cache = cipher.doFinal(data, offSet, MAX_ENCRYPT_BLOCK);  
            } else {  
                cache = cipher.doFinal(data, offSet, inputLen - offSet);  
            }  
            out.write(cache, 0, cache.length);  
            i++;  
            offSet = i * MAX_ENCRYPT_BLOCK;  
        }  
        byte[] encryptedData = out.toByteArray();  
        out.close();  
        return encryptedData;  
    }  
  
    /** 
     * <p> 
     * 私钥加密 
     * </p> 
     *  
     * @param data 
     *            源数据 
     * @param privateKey 
     *            私钥(BASE64编码) 
     * @return 
     * @throws Exception 
     */  
    public static byte[] encryptByPrivateKey(byte[] data, String privateKey)  
            throws Exception {  
        byte[] keyBytes = Base64Utils.decodeFromString(privateKey);
        PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);  
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);  
        Key privateK = keyFactory.generatePrivate(pkcs8KeySpec);  
        Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());  
        cipher.init(Cipher.ENCRYPT_MODE, privateK);  
        int inputLen = data.length;  
        ByteArrayOutputStream out = new ByteArrayOutputStream();  
        int offSet = 0;  
        byte[] cache;  
        int i = 0;  
        // 对数据分段加密  
        while (inputLen - offSet > 0) {  
            if (inputLen - offSet > MAX_ENCRYPT_BLOCK) {  
                cache = cipher.doFinal(data, offSet, MAX_ENCRYPT_BLOCK);  
            } else {  
                cache = cipher.doFinal(data, offSet, inputLen - offSet);  
            }  
            out.write(cache, 0, cache.length);  
            i++;  
            offSet = i * MAX_ENCRYPT_BLOCK;  
        }  
        byte[] encryptedData = out.toByteArray();  
        out.close();  
        return encryptedData;  
    }  
  
    /** 
     * <p> 
     * 获取私钥 
     * </p> 
     *  
     * @param keyMap 
     *            密钥对 
     * @return 
     * @throws Exception 
     */  
    public static String getPrivateKey(Map<String, Object> keyMap)  
            throws Exception {  
        Key key = (Key) keyMap.get(PRIVATE_KEY);  
        return Base64Utils.encode(key.getEncoded()).toString();
    }  
  
    /** 
     * <p> 
     * 获取公钥 
     * </p> 
     *  
     * @param keyMap 
     *            密钥对 
     * @return 
     * @throws Exception 
     */  
    public static String getPublicKey(Map<String, Object> keyMap)  
            throws Exception {  
        Key key = (Key) keyMap.get(PUBLIC_KEY);  
        return Base64Utils.encode(key.getEncoded()).toString();
    }  
      
    /** 
     * 将加密后的字节数组转换为对象 
     *  
     * @MethodName: bytesToString  
     * @Description:  
     * @param encrytpByte 
     * @return 
     * @throws 
     */  
    public static String bytesToString(byte[] encrytpByte) {  
         String result = "";  
         for (Byte bytes : encrytpByte) {  
             result += bytes.toString() + " ";  
         }  
         return result;  
     }  
      
    /** 
     * 公钥加密 
     *  
     * @MethodName: encrypt  
     * @Description:  
     * @param publicKey 
     * @param obj 
     * @return 
     * @throws 
     */  
    public static byte[] encrypt(RSAPublicKey publicKey, byte[] obj) {  
         if (publicKey != null) {  
             try {  
                 Cipher cipher = Cipher.getInstance(KEY_ALGORITHM);  
                 cipher.init(Cipher.ENCRYPT_MODE, publicKey);  
                 return cipher.doFinal(obj);  
             } catch (Exception e) {  
                 e.printStackTrace();  
             }  
         }  
         return null;  
     }  
      
    /** 
     * 私钥加密 
     *  
     * @MethodName: decrypt  
     * @Description:  
     * @param privateKey 
     * @param obj 
     * @return 
     * @throws 
     */  
    public static byte[] decrypt(RSAPrivateKey privateKey, byte[] obj) {  
         if (privateKey != null) {  
             try {  
                 Cipher cipher = Cipher.getInstance(KEY_ALGORITHM);  
                 cipher.init(Cipher.DECRYPT_MODE, privateKey);  
                 return cipher.doFinal(obj);  
             } catch (Exception e) {  
                 e.printStackTrace();  
             }  
         }  
         return null;  
     }  
  
}  